strange USB mouse detection behaviour

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Hello,

I'm using FreeBSD 6.0-RELEASE (generic kernel) on my laptop Compaq Evo 
n1020v and have trouble with Microsoft USB mouse: Mouse is not 
recognized (no /dev/ums0 information in dmesg). Only this trick help me 
to recognize it: When mouse is unplugged and then plugged in back to 
another USB connector while running FreeBSD! /dev/ums0 is available and 
mouse is working perfect!

With Logitech USB mouse it is the same.

Is there somebody who can help me?

Thank you

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